HP Laserjet 4 Manual

Formatter Cage Removal
NoteYou may wisht to remove the metal cover (on the
lower right side) and the power supply for easier
access to the Formatter Cage screws.
1Remove the Right Side Cover and the Top Cover.
2LaserJet 4 and 5: Remove the (7) screws (6 screws in the LJ
5) shown in Figure 6-24a.  (2) screws are on the right rear of
the printer, (1) screw is under the lower front of the Formatter
Cage (except LJ 5). 
LaserJet 4 Plus: Remove the (3) screws shown in Figure
6-24b (one screw is located behind...

Figure 6-24b Formatter Cage Screws (Right Side View -
LaserJet 4 Plus)
Figure 6-24c Formatter Cage Screws (Rear View - LaserJet 4
Plus)
6-28 Removal and Replacement 

Formatter PCA Removal 
CautionThe Formatter PCA is very sensitive to Electro-
static Discharge (ESD) damage. Observe proper
ESD procedures when servicing the printer.
NoteBefore removing the old Formatter PCA, print a
05 SELF TEST to check the current printer page
count, if possible.  If a self test is not possible,
enter the Service Mode, if possible, to display the
page count (see “Service Mode” in Chapter 3).
Remove the Formatter Cage from the printer before beginning
the Formatter PCA removal...

LaserJet 4 Formatter PCA:
1Remove any MIO or SIMM modules from the Formatter
Assembly.
2Remove the (2) black screws from the side of the Formatter
Cage (see Figure 6-25a, callout 1).  
3Remove the MIO Connector Support Bracket (see Figure
6-25a, callout 2).
4Remove the (2) Formatter PCA mounting screws (see
Figure 6-25a callout 3).
(continued on next page)
Figure 6-25a Formatter Cover and PCA Mounting Screws
(LaserJet 4)
6-30 Removal and Replacement 

5Remove the (4) Interface Connector Support Screws from the
rear of the Formatter Cover. The RS-232 connector is held
with 5mm hex-head cap screws (see Figure 6-25b, callout 1).
The parallel connector (see Figure 6-25b, callout 2.) is held in
place with Phillips screws.
6Remove the Formatter PCA.
NoteWhen replacing the Formatter Assembly be sure
to reinstall all SIMM modules and MIO cards.  Be
sure to reset the page count and the Cold Reset
paper size after replacing the Formatter.
(continued on next...

LaserJet 4 Plus and 5 Formatter PCA
1Remove any MIO or SIMM modules from the Formatter
Assembly.
2Remove the MIO Connector Support Bracket (see
Figure 6-25a, callout 2).
3Remove the (4) I/O screws (see Figure 6-26 callout 1).
4Remove the (2) Formatter PCA mounting screws (see
Figure 6-26 callout 2).
NoteWhen replacing the Formatter Assembly be sure
to re-install all SIMM modules and MIO cards.
Be sure to reset the page count and the Cold
Reset paper size after replacing the Formatter.
Figure 1-26...

DC Controller Removal
NoteNote the cable routing before beginning this
disassembly procedure.  Be careful not to damage
the cables during re-assembly.
1Remove the Right Side and the Top Cover Assemblies.
2Remove the Formatter Cage Assembly.
3Remove the 6-wire connector from the Power Supply.
4Remove the plastic DC Controller cover (LaserJet 4 Plus).
5Remove the DC Controller connectors (see Figure 6-27a or
6-27b, callout 1). 
6Release the DC Controller from its retaining clips (2) and
remove the DC...

Figure 1-27b DC Controller Connectors/Retaining Clips
(LaserJet 4 Plus/5)
6-34 Removal and Replacement 

DC Controller Installation     
CautionWhen reinstalling the DC Controller PCA it is
extremely important that all cables be properly
routed.  If cables are not routed properly, it is
difficult to reinstall the Formatter Cage and cable
damage may result.
When replacing the DC Controller, be sure to set the leading edge
adjustment as shown in the following procedure.
NoteThe Leading Edge Adjustment is set at the
factory and is not required as a maintenance
procedure. The Leading Edge Adjustment should
be...

Figure 1-28 Leading Edge Registration Adjustment
Dimensions
Figure 1-29 VR202 Settings (LaserJet 4 shown)
6-36 Removal and Replacement